Display apparatus having right-hand and left-hand illumination units

ABSTRACT

The invention relates to a display apparatus with a display unit, having means for background lighting at the back of the display apparatus. According to the invention, the means for background lighting comprise two illumination units being provided at the right-hand and left-hand of the display apparatus, said illumination units being formed as substantially vertically positioned, longitudinal light guides comprising means for coupling out light, each of the light guides being provided on at least one of its ends with a light source. The light sources preferably comprise coloured LEDs.

The invention relates to a display apparatus with a display unit, havingmeans for background lighting at a side or the back of the displayapparatus.

Such a display apparatus is known i.a. from the Utility Modelpublication DE 20002420. This publication discloses a simple backlighting system with limited back lighting possibilities.

The present invention aims at providing an improved display apparatus.To this end, the invention provides a display apparatus as defined inclaim 1. Devices having the claimed features show a much greater impacton the viewer than the prior art display apparatus with the limited backlighting possibilities. This holds especially for display apparatushaving a wide-screen display unit.

The display apparatus according to the present invention has at leasttwo illumination units, which are preferably attached to the back of theapparatus. In a preferred embodiment of two units, the one unit isprovided on the left-hand side of the apparatus and the other unit onits right-hand side. The units are formed as longitudinal light guides,preferably of a synthetic resin, like acrylic resin, which can beprepared by extrusion. The guides in principle can have a cross sectionof any desired shape, but preferably have a circular cross section. Asthe guides are positioned substantially vertical, they are attached tothe apparatus in a mutually parallel orientation. The display apparatusmay have (an) additional illumination unit(s) on top and/or bottomside(s) of the display apparatus. Latter light guides are positionedsubstantially horizontal.

The light guides employed in the display apparatus according to thepresent invention comprise means for coupling out light. It is possibleto use a reflecting body encapsulated in an extruded light guide.Preferably the means for coupling out light are formed as a structureprovided on the surface of the light guide. This can be obtained bysandblasting part of the surface of the light guide according to adesired structure. Alternatively, good results are also obtained byprinting a diffuse reflective layer on the surface of the light guide,or by applying it by means of a sticker. Under these circumstances, itis preferred if the light guides contain a flat outer surface on whichthe desired structure can be applied.

It is noted that different structures for coupling out light from thelight guide can be used. Seen in the length direction of the guide, thestructure can be continuous or discontinuous (‘zebra’ or ‘dotted’ form).In case that one light source is used, the width of a continuousstructure should increase at increased distance from the light source inorder to obtain a continuous light output along the whole length of thelight guide. In case that each of the light guides is provided with alight source at both of its ends, the width of the continuous structurewill be maximal in the middle of the light guide in order to have thecontinuous light output along the length of the light guide. In casethat a discontinuous pattern is used (stripes or dots), a continuouswidth of the stripes or dots with different pitch lengths betweensubsequent stripes or dots can be used in order to obtain the desiredcontinuous light output.

An interesting display apparatus according to the present invention ischaracterized in that that the light guides are rotatable along alongitudinal axis. This feature allows adjustment of the back lightingpattern on wall. This is particularly useful in case that the screen ofthe display apparatus is positioned not parallel to the back wall, butunder a certain angle. In such situation, the user can rotate the lightguides in such way that under operation of the back lighting a spot onthe wall is obtained which is well balanced on both sides of the displayapparatus. By means of this feature, the desired impact on the viewer ismaintained, even when the display apparatus is positioned under an anglewith respect to the back wall.

Another advantageous embodiment of the invented display is characterizedin that the display apparatus comprises means for controlling the colourof the backlight and that the light guides are provided on both endswith a light source, said light source comprising a red, a green and ablue LED. By means of this embodiment, the display unit may producelight, the colour and light intensity of which can be adapted in orderto fit is optimally with the colour of the room in accordance with thewishes of the user.

Interesting is also the embodiment which is characterized in that thedisplay apparatus comprises a control circuit for controlling the colourof each of the light sources in dependence of a colour of a part of thedisplay screen which is close to the light source. With displayapparatus having this feature seem to project an additional part of thescene displayed on the apparatus in a dynamic way on the back wall. Ithas been shown that the dynamic spot displayed on the wall induces anextraordinary great impact on the viewer, as in this way the sceneobserved seems to be increased.

These and other aspects of the invention will be apparent from andelucidated with reference to the embodiments described hereinafter and adrawing, in which:

FIG. 1 shows an embodiment of a display apparatus according to thepresent invention;

FIG. 2 shows a schematic top view of the display apparatus according tothe invention as shown in FIG. 1;

FIG. 3 shows a detail of the display apparatus according to theinvention as depicted in FIG. 1;

FIG. 4 shows a block diagram of a first embodiment of a control circuitfor use in a display apparatus according to the invention;

FIG. 5 shows another embodiment of a display apparatus according to thepresent invention.

The Figures are purely diagrammatic and not drawn true to scale.Dimensions may be exaggerated for reasons of clarity. In the Figuresequivalent parts have been given as much as possible the same referencenumber.

The display apparatus (1) as shown in FIGS. 1 and 2 is preferablymounted by mounting means (2) to a wall (3) of a room. According to thepresent invention, attached to its back, the display apparatus comprisetwo illumination units (4) for providing a background light formed astwo spots (5) on wall (3). These spots (5) are displayed at theleft-hand side and the right-hand side of the display apparatus. Usuallythey are only displayed during operation of the display apparatus.However it is also possible to display them during the time that thedisplay apparatus is switched off.

FIG. 3-A shows a front view of an illumination unit (4), which can beused in the display apparatus according to the present invention. Theunit comprises longitudinal light guide (6) having a cylindrical form.The surface of the unstructured light guide is polished in order toprevent coupling out of light inserted in the guide during operation. Inthe present case, the light guide is made of an acrylic resin (PMMA,poly-methyl-methacrylate) by means of extrusion. On a flat part of itssurface, a longitudinal structure (7) is prepared by means of printing.This structure causes that part of the light being inserted in the guideis coupled out. Light can be coupled in at a flat end (8) of the lightguide by means of light source (9). This light source can be anincandescent lamp or a halogen lamp. However, it is preferred to use oneor more LEDs (10) for this purpose. In the present embodiment the lightsource consists of a set of three LEDs (10), the individual LEDsemitting Red, Blue and Green light.

During operation of the illumination unit (4), a certain amount of lightenters the light guide (6) generated by LEDs (10) via flat end (8). Bymeans of longitudinal structure (7) part of the inserted light iscoupled out of the light guide in a direction substantiallyperpendicular to the longitudinal axis of the light guide (6). In orderto keep the amount of light coupled out substantially constant over thewhole length of the guide, the width of the coupling out structureincreases as the distant from the light source to the coupling out areaincreases.

FIG. 3-B shows an alternative illumination unit (4), which comprises twolight sources (9) per light guide (6). Again in this example the use ofLEDs as light source are preferred over the use of alternative lightsources. In order to achieve a constant out coupling of light duringoperation of the light guide, the width of the applied coupling outstructure is maximal in the middle of the light guide.

FIG. 3-C shows another alternative illumination unit (4), whichcomprises a single light source (6) having a single Blue LED (10). Inthis example a discontinuous, zebra-like coupling out structure (7) isused in order to keep the light output constant along the length of thelight guide. This structure is prepared by sandblasting the desiredlines of the coupling out structure in the coupling out light guide. Inthis embodiment, the lines have equal width and equal length. The personskilled in the art can of course design alternative structures in whichthe lines have different length and widths and in which the distancebetween neighbouring lines are adjusted to these alternative structures.

In general, the structure is applied in such way that the light beamcoupled out from the light guide emits under an angle of 50-90 degrees.An optimal effect is however reached in case that said angle is 70degrees with a deviation of maximally 10 degrees, preferably 5 degrees.

Returning to FIG. 2, it is stressed that the illumination units (4) canbe rotated along the longitudinal axis of the light guides, as indicatedby the arrows. In case that the display apparatus is positioned under anangle with respect to the wall (i.e. the plane of the screen of thedisplay apparatus is not parallel to the plane of the wall), the lightspots (5) displayed on the wall during operation of the apparatus can beadjusted manually by the user in order to give them an optimal shape.This holds both for TV-sets or monitors that are attached to the walland for apparatus standing free of the wall. In practise the lightguides can be clamped in one or more settings, which allows rotation ofthe guides along their longitudinal axis.

The display indicated comprises means for controlling the colour of thebacklight. The colour produced by the illumination unit of a displayapparatus without such controlling means can be neutral white or astatic colour. However it is preferred that the illumination unitproduces during operation coloured light, the wavelength and brightnessof which can be adjusted by the user according to his wishes. To thisend, the display apparatus has a control unit CU that produces red,green and blue control signals RCS, GCS, BCS that control red, green andblue LEDs (10) of the illumination units (4). The control unit CUreceives a user control signal UCS (that may be produces by a remotecontrol signal reception device) to set the colour in such a manner thatit fits in with the wish of the user. A block diagram for thisembodiment is shown in FIG. 4. While the illumination unit preferablyemploys LEDs, other light sources may also be used instead inalternative embodiments. The control unit may receive a signal from alight sensor so as to make the light from the illumination unitdependent on ambient light as well.

FIG. 5 shows a further interesting embodiment of a display according tothe present invention, which is characterized in that the displayapparatus comprises a control circuit for controlling the colour of eachof the light sources in dependence of a colour of a part of the displayscreen, which is close to the light source. More particularly it shows afront view of a display apparatus (1) with a display screen (11) and twoillumination units (4) on the left-hand and the right-hand side of theapparatus. Each of the illumination units (4) comprises a longitudinallight guide with a light source (9) on each of both ends of the lightguides. Said light sources are composed of three LEDs emitting blue,green and red light.

The display apparatus also comprises a circuit for controlling thecolour of the light sources. To this end, the display apparatus has acontrol unit CU that produces red, green and blue control signals RCS,GCS, BCS that control the average colour produced by the red, green andblue LEDs (10) of one of the four light sources of the two illuminationunits (4). The control unit CU receives a control signal UCS to set thecolour of one of the light sources, which signal is dependent on theaverage colour of one of the segments (12), (13), (14) or (15) of screen(11) or of a part thereof. Thus the produced colour of the light sourceof each of the four light sources is dependent on the average colour ofthe segment, which is closest to the light source. It is stressed thatnot only an average colour can be selected in this way, but also adominant colour, this all upon the wish of the user.

Due to colour mixing in the longitudinal light guides, a smooth colourtransition between both ends of the light guides is obtained. Thus incase of a picture of the beach, both top segments 12 and 13 areessentially blue and the light sources on top of both light guides willproduce essentially blue light. Both bottom segments are howeveressentially yellow, and the light sources on bottom of both light guideswill produce essentially yellow light. In the light guides a transitionfrom top (blue) to bottom (yellow) is obtained for such picture. Thiscolour transition is displayed on the wall. It appears that this kind ofdynamic back lighting in a display causes a very impressive impact onthe viewer. It essentially broadens the width of the scene displayed onthe display apparatus.

It should be noted that the above-mentioned embodiments illustraterather than limit the invention, and that those skilled in the art willbe able to design many alternative embodiments without departing fromthe scope of the appended claims. In the claims, any reference signsplaced between parentheses shall no be construed as limiting the claim.Use of the verb ‘comprise’ and it conjugations does not exclude thepresence of elements or steps other than those stated in a claim. Thearticle ‘a’ or ‘an’ preceding an element does not exclude the presenceof a plurality of such elements. The invention may be implemented bymeans of hardware comprising several distinct elements and by means of asuitable programmed computer. In the device claim enumerating severalmeans, several of these means may be embodied by one and the same itemof hardware. The mere fact that certain measures are recited in mutuallydifferent dependent claims does not indicate that a combination of thesemeasures cannot be used to advantage.

1. A display apparatus with a display unit, having means for backgroundlighting at a side or the back of the display apparatus to produce aback light pattern; characterized in that the means for backgroundlighting comprise two illumination units being provided at theright-hand and left-hand of the display apparatus, said illuminationunits being formed as substantially vertically positioned, longitudinallight guides comprising means for coupling out light, each of the lightguides being provided on at least one of its ends with a light source;further characterized in that the light guides are rotatable along alongitudinal axis to thereby allow adjustment of the back light pattern,wherein said rotation of each light guide is performed independently ofany movement of the light guide's corresponding light source.
 2. Adisplay apparatus according to claim 1, characterized in that the meansfor coupling out light are formed as a structure provided on the surfaceof the light guide.
 3. A display apparatus according to claim 1,characterized in that the display apparatus comprises means forcontrolling the colour of the backlight and that the light guides areprovided on both ends with a light source, said light source comprisinga red, a green and a blue LED.
 4. A display apparatus according to claim3, characterized in that the display apparatus comprises a controlcircuit for controlling the colour of each of the light sources independence of a colour of a part of the display screen which is close tothe light source.
 5. A display apparatus with a display unit, havingmeans for background lighting at a side or the back of the displayapparatus; characterized in that the means for background lightingcomprise two illumination units being provided at the right-hand andleft-hand of the display apparatus, said illumination units being formedas substantially vertically positioned, longitudinal light guidescomprising means for coupling out light, each of the light guides beingprovided on at least one of its ends with a light source; furthercharacterized in that the light guides are rotatable along alongitudinal axis to thereby allow adjustment of the back light pattern,wherein said rotation of each light guide is performed independently ofany movement of the light guide's corresponding light source; furthercharacterized in that the means for background lighting produces a backlight pattern on a wall.
 6. A display apparatus according to claim 5,characterized in that the means for coupling out light are formed as astructure provided on the surface of the light guide.
 7. A displayapparatus according to claim 5, characterized in that the displayapparatus comprises means for controlling the colour of the backlightand that the light guides are provided on both ends with a light source,said light source comprising a red, a green and a blue LED.
 8. A displayapparatus according to claim 7, characterized in that the displayapparatus comprises a control circuit for controlling the colour of eachof the light sources in dependence of a colour of a part of the displayscreen which is close to the light source.
 9. A display apparatus with adisplay unit, having means for background lighting at a side or the backof the display apparatus to produce a back light pattern; characterizedin that the means for background lighting comprise two illuminationunits being provided at the right-hand and left-hand of the displayapparatus, said illumination units being formed as substantiallyvertically positioned, longitudinal light guides comprising means forcoupling out light, each of the light guides being provided on both endswith a light source; wherein the display apparatus further comprisesmeans for controlling the color of the background lighting, and acontrol circuit for controlling the color of each of the light sourcesin dependence upon a color of a part of the display unit which is closeto the light source, characterized in that the display apparatus furthercomprises user controlled means for adjusting the wavelength andbrightness of the color of the background lighting.
 10. A displayapparatus according to claim 9 wherein the means for coupling out lightare formed as a structure provided on the surface of the light guide.11. A display apparatus according to claim 9 wherein the light guidesare rotatable along a longitudinal axis.